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Exam Code: JN0-664

Exam Name: Service Provider Routing and Switching, Professional (JNCIP-SP)

Certification Provider: Juniper

Corresponding Certification: JNCIP-SP

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Juniper JN0-664 Practice Test 21

Question 200

An IS-IS L1 area includes multiple ABRs injecting external routes. Observed: A critical prefix from Level 2 appears in one branch with a problematic metric. What operational check best guards against this problem returning?

  1. For each approved related change, verify that the permitted branch route has stable and correct cost across the area. Flag recurrence if a critical prefix from Level 2 appears in one branch with a problematic metric.
  2. For each approved related change, verify that branch default chooses the planned reachable gateway and avoids unexpected detours. Flag recurrence if traffic consistently uses the farther gateway despite the closer one being healthy.
  3. For each approved related change, verify that all required prefix TLVs appear across receiving LSDBs without LSP truncation. Flag recurrence if several IS-IS devices omit recently advertised routes during peak growth.
  4. For each approved related change, verify that both approved next hops appear with safe load distribution and failover. Flag recurrence if the backup next hop is not in the routing table despite physical path diversity.

Explanation

Correct Answer

A:

This control asks for the same recovery evidence (The permitted branch route has stable and correct cost across the area) and flags recurrence of the same failure (A critical prefix from Level 2 appears in one branch with a problematic metric). It targets the underlying issue, route leaking policy and metric adjustment are inconsistent among l1/l2 routers, rather than a different service problem. The exact cadence must be agreed with operations.

Incorrect Answers

B:

The proposed control is tied to attached-bit and default-cost selection ignore intended internal metric planning, typically observed when traffic consistently uses the farther gateway despite the closer one being healthy. Here the target is route leaking policy and metric adjustment are inconsistent among l1/l2 routers; monitor the permitted branch route has stable and correct cost across the area.

C:

It is valid for another service scenario but checks several is-is devices omit recently advertised routes during peak growth. This case instead needs a gate for a critical prefix from level 2 appears in one branch with a problematic metric and evidence that the permitted branch route has stable and correct cost across the area.

D:

This gate monitors a different failure, the backup next hop is not in the routing table despite physical path diversity. It would not detect the current problem: A critical prefix from Level 2 appears in one branch with a problematic metric. The appropriate check requires the permitted branch route has stable and correct cost across the area.

Question 201

An IS-IS topology is expected to support two equal-cost routes to a loopback. Observed: The backup next hop is not in the routing table despite physical path diversity. Which targeted remediation is most appropriate for the observed condition?

  1. Compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design.
  2. Enable supported IS-IS IPv6 reachability on required interfaces and levels.
  3. Check equal accumulated IS-IS costs and supported ECMP settings.
  4. Repair MTU consistency and test hello packet carriage before reestablishing adjacency.

Explanation

Correct Answer

C:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—The backup next hop is not in the routing table despite physical path diversity—is consistent with wide metrics differ or the installed multipath limit excludes an otherwise equal path. Use the specified correction, then verify: Both approved next hops appear with safe load distribution and failover. Preserve existing policy and tenant isolation.

Incorrect Answers

A:

The option may be useful when the interface receives Hellos but no sustained database synchronization, but that is not the current evidence. Here, the backup next hop is not in the routing table despite physical path diversity, indicating wide metrics differ or the installed multipath limit excludes an otherwise equal path. The targeted action is Check equal accumulated IS-IS costs and supported ECMP settings.

B:

This change belongs to a different IS-IS issue: Routers do not install IPv6 interrouter loopback prefixes. That issue involves ipv6 topology or address-family advertisements are not enabled as intended. The current symptom is The backup next hop is not in the routing table despite physical path diversity. It instead requires check equal accumulated IS-IS costs and supported ECMP settings.

D:

This remediates is-is hello packet padding exceeds one path's available frame size, normally indicated by Neighbor remains in initialization and three-way handshake does not complete. It would leave the observed problem (The backup next hop is not in the routing table despite physical path diversity) unresolved. Address it with check equal accumulated IS-IS costs and supported ECMP settings.

Question 202

An IS-IS topology is expected to support two equal-cost routes to a loopback. Observed: The backup next hop is not in the routing table despite physical path diversity. What evidence would validate recovery from this precise failure mode?

  1. The adjacency reaches Up and LSP flooding completes consistently.
  2. The target IPv6 loopbacks install with correct IS-IS next hops.
  3. Neighbor forms at the intended level without padding drops.
  4. Both approved next hops appear with safe load distribution and failover.

Explanation

Correct Answer

D:

The intended result is Both approved next hops appear with safe load distribution and failover. It specifically verifies recovery from wide metrics differ or the installed multipath limit excludes an otherwise equal path, which produced the original symptom: The backup next hop is not in the routing table despite physical path diversity. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

That observation would verify a separate fault involving the peer's link-level settings or level-specific parameters are mismatched. Its symptom is The interface receives Hellos but no sustained database synchronization. For this case the actual issue is wide metrics differ or the installed multipath limit excludes an otherwise equal path, and the relevant success signal is Both approved next hops appear with safe load distribution and failover.

B:

It confirms an unrelated service correction: IPv6 topology or address-family advertisements are not enabled as intended. The present case reports The backup next hop is not in the routing table despite physical path diversity. Its completion test is Both approved next hops appear with safe load distribution and failover.

C:

This result is useful in another case with evidence Neighbor remains in initialization and three-way handshake does not complete. It does not test recovery from the backup next hop is not in the routing table despite physical path diversity. Check instead whether both approved next hops appear with safe load distribution and failover.

Question 203

An IS-IS topology is expected to support two equal-cost routes to a loopback. Observed: The backup next hop is not in the routing table despite physical path diversity. What underlying protocol or service configuration problem best explains the evidence?

  1. IS-IS hello packet padding exceeds one path's available frame size.
  2. IPv6 topology or address-family advertisements are not enabled as intended.
  3. Wide metrics differ or the installed multipath limit excludes an otherwise equal path.
  4. The peer's link-level settings or level-specific parameters are mismatched.

Explanation

Correct Answer

C:

Because the backup next hop is not in the routing table despite physical path diversity, the likely cause is wide metrics differ or the installed multipath limit excludes an otherwise equal path. It is testable: Check equal accumulated IS-IS costs and supported ECMP settings. Expected follow-up: Both approved next hops appear with safe load distribution and failover.

Incorrect Answers

A:

That explanation fits another condition: Neighbor remains in initialization and three-way handshake does not complete. The evidence here is The backup next hop is not in the routing table despite physical path diversity. Its closer root cause is Wide metrics differ or the installed multipath limit excludes an otherwise equal path.

B:

IPv6 topology or address-family advertisements are not enabled as intended. would normally be accompanied by routers do not install ipv6 interrouter loopback prefixes. The observed symptom is different: The backup next hop is not in the routing table despite physical path diversity. The likely cause is Wide metrics differ or the installed multipath limit excludes an otherwise equal path.

D:

The stated cause is possible elsewhere but explains the interface receives hellos but no sustained database synchronization, not the backup next hop is not in the routing table despite physical path diversity. This incident is better attributed to wide metrics differ or the installed multipath limit excludes an otherwise equal path.

Question 204

An IS-IS topology is expected to support two equal-cost routes to a loopback. Observed: The backup next hop is not in the routing table despite physical path diversity. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that the adjacency reaches Up and LSP flooding completes consistently. Flag recurrence if the interface receives Hellos but no sustained database synchronization.
  2. For each approved related change, verify that both approved next hops appear with safe load distribution and failover. Flag recurrence if the backup next hop is not in the routing table despite physical path diversity.
  3. For each approved related change, verify that the target IPv6 loopbacks install with correct IS-IS next hops. Flag recurrence if routers do not install IPv6 interrouter loopback prefixes.
  4. For each approved related change, verify that neighbor forms at the intended level without padding drops. Flag recurrence if neighbor remains in initialization and three-way handshake does not complete.

Explanation

Correct Answer

B:

A useful regression gate tests whether both approved next hops appear with safe load distribution and failover and alerts when the backup next hop is not in the routing table despite physical path diversity. This directly checks the technical weakness: Wide metrics differ or the installed multipath limit excludes an otherwise equal path. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.

Incorrect Answers

A:

The proposed control is tied to the peer's link-level settings or level-specific parameters are mismatched, typically observed when the interface receives Hellos but no sustained database synchronization. Here the target is wide metrics differ or the installed multipath limit excludes an otherwise equal path; monitor both approved next hops appear with safe load distribution and failover.

C:

This gate monitors a different failure, routers do not install ipv6 interrouter loopback prefixes. It would not detect the current problem: The backup next hop is not in the routing table despite physical path diversity. The appropriate check requires both approved next hops appear with safe load distribution and failover.

D:

It is valid for another service scenario but checks neighbor remains in initialization and three-way handshake does not complete. This case instead needs a gate for the backup next hop is not in the routing table despite physical path diversity and evidence that both approved next hops appear with safe load distribution and failover.

Question 205

An IS-IS core receives a newly assigned device with repeated adjacency resets. Observed: The interface receives Hellos but no sustained database synchronization. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Restore a legitimate L1/L2 border adjacency and verify attached-bit default propagation.
  2. Make the customer network passive or remove protocol participation as appropriate.
  3. Compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design.
  4. Enable a valid Level 2 topology at the interarea boundary.

Explanation

Correct Answer

C:

The observed condition is The interface receives Hellos but no sustained database synchronization. That indicates the peer's link-level settings or level-specific parameters are mismatched. Applying the proposed remedy directly changes that condition. A concrete completion check is: The adjacency reaches Up and LSP flooding completes consistently.

Incorrect Answers

A:

This remediates no attached level 1/level 2 router is advertising the appropriate default path, normally indicated by The device has healthy local adjacencies but does not know any Level 2 exit. It would leave the observed problem (The interface receives Hellos but no sustained database synchronization) unresolved. Address it with compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design.

B:

The option may be useful when customer service interface accidentally forms an IS-IS adjacency, but that is not the current evidence. Here, the interface receives Hellos but no sustained database synchronization, indicating the peer's link-level settings or level-specific parameters are mismatched. The targeted action is Compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design.

D:

This change belongs to a different IS-IS issue: Transit prefixes in one area disappear from an adjacent area. That issue involves a router operates only level 1 across a segment requiring level 2 connectivity. The current symptom is The interface receives Hellos but no sustained database synchronization. It instead requires compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design.

Question 206

An IS-IS core receives a newly assigned device with repeated adjacency resets. Observed: The interface receives Hellos but no sustained database synchronization. After the correction, which result would most convincingly show that this fault is resolved?

  1. The adjacency reaches Up and LSP flooding completes consistently.
  2. The L1 router selects a valid nearest Level 2 exit and customer traffic resumes.
  3. No customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.
  4. Remote Level 2 routes are reachable without improperly merging Level 1 areas.

Explanation

Correct Answer

A:

After compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design, inspect whether the adjacency reaches Up and LSP flooding completes consistently. This closes the loop between the reported observation (The interface receives Hellos but no sustained database synchronization) and the underlying issue (The peer's link-level settings or level-specific parameters are mismatched).

Incorrect Answers

B:

This result is useful in another case with evidence The device has healthy local adjacencies but does not know any Level 2 exit. It does not test recovery from the interface receives hellos but no sustained database synchronization. Check instead whether the adjacency reaches Up and LSP flooding completes consistently.

C:

That observation would verify a separate fault involving the customer interface was enabled as an active is-is circuit instead of a passive advertisement. Its symptom is Customer service interface accidentally forms an IS-IS adjacency. For this case the actual issue is the peer's link-level settings or level-specific parameters are mismatched, and the relevant success signal is The adjacency reaches Up and LSP flooding completes consistently.

D:

It confirms an unrelated service correction: A router operates only Level 1 across a segment requiring Level 2 connectivity. The present case reports The interface receives Hellos but no sustained database synchronization. Its completion test is The adjacency reaches Up and LSP flooding completes consistently.

Question 207

An IS-IS core receives a newly assigned device with repeated adjacency resets. Observed: The interface receives Hellos but no sustained database synchronization. Which root cause is most consistent with this symptom?

  1. The customer interface was enabled as an active IS-IS circuit instead of a passive advertisement.
  2. The peer's link-level settings or level-specific parameters are mismatched.
  3. A router operates only Level 1 across a segment requiring Level 2 connectivity.
  4. No attached Level 1/Level 2 router is advertising the appropriate default path.

Explanation

Correct Answer

B:

The reported evidence—The interface receives Hellos but no sustained database synchronization—supports the peer's link-level settings or level-specific parameters are mismatched. The appropriate intervention is to compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design, with confirmation from the adjacency reaches Up and LSP flooding completes consistently. Other causes require actual device-state verification.

Incorrect Answers

A:

The stated cause is possible elsewhere but explains customer service interface accidentally forms an is-is adjacency, not the interface receives hellos but no sustained database synchronization. This incident is better attributed to the peer's link-level settings or level-specific parameters are mismatched.

C:

A router operates only Level 1 across a segment requiring Level 2 connectivity. would normally be accompanied by transit prefixes in one area disappear from an adjacent area. The observed symptom is different: The interface receives Hellos but no sustained database synchronization. The likely cause is The peer's link-level settings or level-specific parameters are mismatched.

D:

That explanation fits another condition: The device has healthy local adjacencies but does not know any Level 2 exit. The evidence here is The interface receives Hellos but no sustained database synchronization. Its closer root cause is The peer's link-level settings or level-specific parameters are mismatched.

Question 208

An IS-IS core receives a newly assigned device with repeated adjacency resets. Observed: The interface receives Hellos but no sustained database synchronization. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that the L1 router selects a valid nearest Level 2 exit and customer traffic resumes. Flag recurrence if the device has healthy local adjacencies but does not know any Level 2 exit.
  2. For each approved related change, verify that no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct. Flag recurrence if customer service interface accidentally forms an IS-IS adjacency.
  3. For each approved related change, verify that remote Level 2 routes are reachable without improperly merging Level 1 areas. Flag recurrence if transit prefixes in one area disappear from an adjacent area.
  4. For each approved related change, verify that the adjacency reaches Up and LSP flooding completes consistently. Flag recurrence if the interface receives Hellos but no sustained database synchronization.

Explanation

Correct Answer

D:

The control is specific to the initial failure. It requires the result The adjacency reaches Up and LSP flooding completes consistently. and treats The interface receives Hellos but no sustained database synchronization. as a failure signal. The causal concern is the peer's link-level settings or level-specific parameters are mismatched.

Incorrect Answers

A:

It is valid for another service scenario but checks the device has healthy local adjacencies but does not know any level 2 exit. This case instead needs a gate for the interface receives hellos but no sustained database synchronization and evidence that the adjacency reaches Up and LSP flooding completes consistently.

B:

The proposed control is tied to the customer interface was enabled as an active is-is circuit instead of a passive advertisement, typically observed when customer service interface accidentally forms an IS-IS adjacency. Here the target is the peer's link-level settings or level-specific parameters are mismatched; monitor the adjacency reaches Up and LSP flooding completes consistently.

C:

This gate monitors a different failure, transit prefixes in one area disappear from an adjacent area. It would not detect the current problem: The interface receives Hellos but no sustained database synchronization. The appropriate check requires the adjacency reaches Up and LSP flooding completes consistently.

Question 209

An upstream eBGP link migrates to a new provider router. Observed: BGP remains Idle even though next-hop IPs respond to ping. What should the routing engineer change first to address this particular symptom?

  1. Coordinate a matched BGP authentication key change on both peers.
  2. Align neighbor addresses and peer AS configuration with the authorized session design.
  3. Explicitly permit only authorized customer announcements and reject internal infrastructure routes.
  4. Enable the intended multiprotocol IPv6 unicast family on both neighbors.

Explanation

Correct Answer

B:

The decisive evidence is that BGP remains Idle even though next-hop IPs respond to ping. This follows from the remote neighbor ip or expected autonomous-system setting does not match the peering contract. The focused remedy is to align neighbor addresses and peer AS configuration with the authorized session design. Confirm improvement when the intended external BGP session establishes and the agreed routes appear. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This change belongs to a different BGP issue: Logs record authentication failures immediately after a key rotation. That issue involves tcp md5 authentication keys differ between the two bgp endpoints. The current symptom is BGP remains Idle even though next-hop IPs respond to ping. It instead requires align neighbor addresses and peer AS configuration with the authorized session design.

C:

This remediates bgp export policy is too broad for the neighbor's contractual prefix set, normally indicated by The transit edge begins advertising an infrastructure loopback to an external customer. It would leave the observed problem (BGP remains Idle even though next-hop IPs respond to ping) unresolved. Address it with align neighbor addresses and peer AS configuration with the authorized session design.

D:

The option may be useful when the IPv4 BGP session is Established but IPv6 route exchange never starts, but that is not the current evidence. Here, bGP remains Idle even though next-hop IPs respond to ping, indicating the remote neighbor ip or expected autonomous-system setting does not match the peering contract. The targeted action is Align neighbor addresses and peer AS configuration with the authorized session design.

Question 210

An upstream eBGP link migrates to a new provider router. Observed: BGP remains Idle even though next-hop IPs respond to ping. Which acceptance observation best confirms that the proposed change worked?

  1. Session reaches Established with no continuing TCP authentication errors.
  2. The intended external BGP session establishes and the agreed routes appear.
  3. Remote customer sees its contracted prefixes without provider loopbacks.
  4. IPv6 NLRI appears with reachable IPv6 next hops while IPv4 remains stable.

Explanation

Correct Answer

B:

This acceptance criterion tests the actual fault. The source evidence was BGP remains Idle even though next-hop IPs respond to ping. The correction addresses the remote neighbor ip or expected autonomous-system setting does not match the peering contract; success requires the intended external BGP session establishes and the agreed routes appear.

Incorrect Answers

A:

It confirms an unrelated service correction: TCP MD5 authentication keys differ between the two BGP endpoints. The present case reports BGP remains Idle even though next-hop IPs respond to ping. Its completion test is The intended external BGP session establishes and the agreed routes appear.

C:

This result is useful in another case with evidence The transit edge begins advertising an infrastructure loopback to an external customer. It does not test recovery from bgp remains idle even though next-hop ips respond to ping. Check instead whether the intended external BGP session establishes and the agreed routes appear.

D:

That observation would verify a separate fault involving ipv6 address-family activation is missing for that neighbor. Its symptom is The IPv4 BGP session is Established but IPv6 route exchange never starts. For this case the actual issue is the remote neighbor ip or expected autonomous-system setting does not match the peering contract, and the relevant success signal is The intended external BGP session establishes and the agreed routes appear.

Service Provider Routing and Switching, Professional (JNCIP-SP) (JN0-664) Practice Tests